The present invention relates to electromechanical transducers and in particular to an audio transducer that may be applied directly to the eardrum.
Audio transducers convert electrical signals, for example, music or spoken voice, into audio waveforms perceptible by the human ear. A common audio transducer such as a “loudspeaker” provides an electric actuator such as a coil/magnet pair or piezoelectric material coupled to a diaphragm/horn providing coupling between the actuator and air.
Current hearing aids may employ a compact loudspeaker design converting electrical signals into pressure waves in the air that travel down the ear canal to induce vibrations in the eardrum (tympanic membrane). These vibrations are then conducted mechanically through structure of the inner ear, which can detect vibrations by special nerve cells. This need to couple the acoustic energy of the loudspeaker into the air increases the bulk of a hearing aid (required for the diaphragm/horn structure), which causes conversion inefficiencies, increasing the demand on and reducing the Life of the hearing-aid batteries.
U.S. Pat. No. 9,532,150, assigned to the assignee of the present application and hereby incorporated by reference, teaches an audio transducer with an electric actuator that can be applied directly to the eardrum, eliminating the need for the diaphragm/horn structure for coupling acoustic energy into the air. The ability to actuate this transducer, for example, wirelessly, raises the possibility of extremely compact and unobtrusive hearing aid designs.
The desirably small size of the electric actuator that can be supported on the eardrum and the likely low voltages available for driving that actuator present challenges with respect to providing sufficient stimulation of the eardrum for the hearing impaired.